Add ServletContextListener to embedded web app

* User can add @Bean of type EventListener (e.g.
ServletContextListener)

[Fixes #54112999] [bs-254]

spring-boot-samples/spring-boot-sample-tomcat/src/main/java/org/springframework/boot/sample/tomcat/SampleTomcatApplication.java

@@ -16,8 +16,14 @@
 
 package org.springframework.boot.sample.tomcat;
 
+import javax.servlet.ServletContextEvent;
+import javax.servlet.ServletContextListener;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.ComponentScan;
 import org.springframework.context.annotation.Configuration;
 
@@ -26,8 +32,25 @@ import org.springframework.context.annotation.Configuration;
 @ComponentScan
 public class SampleTomcatApplication {
 
+	private static Log logger = LogFactory.getLog(SampleTomcatApplication.class);
+
 	public static void main(String[] args) throws Exception {
 		SpringApplication.run(SampleTomcatApplication.class, args);
 	}
 
+	@Bean
+	protected ServletContextListener listener() {
+		return new ServletContextListener() {
+			@Override
+			public void contextInitialized(ServletContextEvent sce) {
+				logger.info("ServletContext initialized");
+			}
+
+			@Override
+			public void contextDestroyed(ServletContextEvent sce) {
+				logger.info("ServletContext destroyed");
+			}
+		};
+	}
+
 }